Synthesis of hollow lantern-like Eu(III)-doped g-C3N4 with enhanced visible light photocatalytic perfomance for organic degradation

doi:10.1016/j.jhazmat.2018.01.058

Journal of Hazardous Materials

Volume 349, 5 May 2018, Pages 224-233

https://doi.org/10.1016/j.jhazmat.2018.01.058 Get rights and content

Highlights

•
The hollow lantern-like Eu(III)-doped g-C₃N₄ was successfully synthesized.
•
Eu-doped g-C₃N₄ exhibited enhanced photocatalytic activity for TC and RhB degradation.
•
The enhanced photocatalytic efficiency is ascribed to the synergy effect of Eu(III) and the hollow structures.
•
The photo-degradation is dominant by O₂⁻ and OH radicals.

Abstract

A series of hollow structure lantern-like Eu(III)-doped g-C₃N₄ (xEu-CN, x = 1, 2, 3) was firstly synthesized by heating a mixture of melamine, HNO₃ and Eu₂O₃ at 500 °C for 2 h. The phase, morphology and optical properties of the serial xEu-CN samples were characterized by different techniques, including TEM, XRD, FT-IR, SEM, XPS, BET, UV–vis, PL, photocurrent, and EIS. The results indicated that Eu doping extraordinarily enhanced the photocatalytic activity of pure g-C₃N₄, and the 2Eu-CN exhibited the highest photocatalytic performance with a 98% (82%) degradation rate for RhB (TC), 6.03 (1.71)-fold of pure g-C₃N₄(CN). The higher photocatalytic efficiency is ascribed to the synergy effect of Eu(III) and the hollow structures, which led to a larger surface specific area, bandgap narrowing, enhanced light harvesting ability and efficient charge separation.

Introduction

Visible light photocatalysis has widely attracted interest due to it exhibits fascinating application prospects in energy, pollution degradation and environmental remediation [1,2]. Among the numerous existing photocatalysts, a metal-free semiconductor, graphitic carbon nitride (g-C₃N₄) has drawn increasing attention due to its relative facile synthesis, low costs, a unique two-dimensional structure, and excellent chemical stability [[3], [4], [5], [6]]. After the first report on g-C₃N₄ in 2009 [7], although large amounts of research have been focused on developing g-C₃N₄ derivatives, the photocatalytic performances of pristine bulk g-C₃N₄ have been largely hindered because of the high recombination rate of photoexcited electron-hole pairs, low quantum efficiency, and low specific surface area [8,9]. Thus, to solve these problems, various approaches have been explored, such as, enhancing specific surface areas, controlling the morphology, and doping with metal or nonmetal species [[10], [11], [12]].

Among various strategies, metal doping is an effective and conventional method to boost the photocatalytic activity generation over g-C₃N₄ photocatalysts, which can simultaneously achieve the promoted charge separation, accelerated surface reaction kinetics, and suppressed surface back reactions [[13], [14], [15], [16], [17]]. To date, various types of co catalysts, such as, K, Ag, Mn, Fe, Ni, Cu, and Co, etc and their compounds have been doped into g-C₃N₄ to obtain the improved H₂ evolution [[13], [14], [15], [16], [17]]. Among these metal elements, the rare earth ions that have characteristic of incompletely occupied 4f and empty 5d orbitals, which can be the centre of electron capture and increase the optical absorption ability, is extremely attractive for elevating the photocataltyic activity of catalysts [18]. The Eu³⁺ ion, an important rare earth ion, has an unfilled 4f shell and the Eu³⁺ ions can feasibly capture photoinduced electrons [19]. However, there are few reports about Eu doped g-C₃N₄ up to now, except that by Xu et al. [20], who synthesized Eu doped graphitic carbon nitride. The results verified that europium doping can effectively increase the photocatalytic activity of g-C₃N₄ and that the sample with the europium doping content of 0.38 wt.% possessed the highest photocatalytic performance. However, it is a pity that the specific surface area only increased from 12 m²/g for g-C₃N₄ to 23 m²/g for 0.38 wt.% Eu doped CN. Therefore, it is desirable to develop a facile synthesis method for Eu doped g-C₃N₄ with a larger specific surface area.

In addition to metal doping, enlarging the specific surface area of the catalysts is another effective way to elevate the photocatalytic efficiency of g-C₃N₄. In recent years, hollow structures photocatalyst materials, which exhibited increased surface-to-volume ratio, more reaction active centers and reduced the charge and mass diffusion lengths, have attracted substantial attention owing to their outstanding features of low density, and enhanced surface area [21,22]. To date, large numbers of synthetic techniques have been developed to synthesize hollow-structured samples, such as soft- and hard-template methods, emulsion techniques, and molecular self-assembly, and so on. Despite the great progress in these methods, some shortcomings, such as pullutants would produce during or after the template etching process for hard template method [23,24], weak stability and low efficiency for soft templates method [25,26], and limited increase of surface areas and low operating control ability for molecular self-assembly method [27,28], which are hurdles for the practical and scalable application of these methods.

Herein, in the current study, a novel hollow-structured lantern-like Eu-doped g-C₃N₄ (Eu-CN) photocatalyst with a large specific surface area (137.2 m²/g) and high photocatalysis efficiency is firs fabricated via a simple and facile one-step process, ie. thermal polycondensation. There are very few reports in the literature about Eu-doped hollow-structured lantern-like g-C₃N₄ synthesis. The photocatalytic activity of a hollow-structured Eu-doped lantern-like g-C₃N₄ photocatalyst was tested via the photodegradation of rhodamine B (RhB) and tetracycline(TC) illuminated under visible light. The results showed that hollow-structured Eu doped lantern-like g-C₃N₄ displayed a higher photocatalytic decomposition rate towards RhB and TC compared to the pristine g-C₃N₄ sample. The effects of Eu doping on the g-C₃N₄ structure and catalytic performance and the Eu doping amount were discussed through the use of all types of characterization techniques and the photocatalytic degradation of RhB and TC solution under visible light irradiation. Meanwhile, the stability of the photocatalysts and the reaction radical species were investigated via the experimental results.

Section snippets

Photocatalyst preparation

Some amount of Eu₂O₃ powder was dissolved in 15 mL of dilute nitric acid (20%), and then 4 g of melamine powder was added to the solution and magnetically stirred to obtain a white pasty solid. The prepared white solid mixture was put into a 30 mL cubicle with a cover, placed into a muffle furnace at 200 °C and then further heated to 500 °C at a rate of 10 °C min. After maintaining the temperature at 500 °C for 2 h, the crucible was taken out immediately to cool naturally, and a sample of

Structure and morphology

To study the effects of Eu doping on the crystal phase structure of g-C₃N₄, XRD measurements were carried out. Fig. 1a displays the XRD patterns of the pure g-C₃N₄ and series of Eu-doped g-C₃N₄ hybrid photocatalysts. As shown in Fig. 1a, all obtained powder samples exhibited two distinct diffraction peaks centered at approximately 27.4° and 13.1°, which are consistent with the previously reported values for the hexagonal phase of polymeric g-C₃N₄ (JCPDS NO. 87-1526), confirming the formation of

Conclusions

In summary, the hollow structure lantern-like Eu doped g-C₃N₄ was successfully prepared by heating a melamine, Eu₂O₃ and HNO₃ mixture at 500 °C for 2 h. Eu -doped g-C₃N₄ did not exhibit a change in phase or structure but did exhibit an apparent morphological change, that is a novel hollow lantern-like morphology appeared that benefited enhanced specific surface area and photogenerated electron transport. Furthermore, the enhanced light harvesting ability, narrower band-gap, and increased charge

Acknowledgements

This work was supported by the National Natural Science Foundation of China for Youth (21207093), and Liaoning Excellent Talents in University(LJQ2014023).

References (42)

H. Jiang et al.
Enhanced photoactivity of Sm, N, P-tridoped anatase-TiO₂ nano-photocatalyst for 4-chlorophenol degradation under sunlight irradiation
J. Hazard. Mater.
(2013)
M. Wang et al.
Effects of Cu dopants on the structures and photocatalytic performance of cocoon-like Cu-BiVO₄ prepared via ethylene glycol solvothermal method
J. Alloys Compd.
(2013)
W. Cui et al.
Steering the interlayer energy barrier and charge flow via bioriented transportation channels in g-C₃N₄: enhanced photocatalysis and reaction mechanism
J. Catal.
(2017)
Y. Zhou et al.
N-doped graphitic carbon-incorporated g-C₃N₄ for remarkably enhanced photocatalytic H₂ evolution under visible light
Carbon
(2016)
B. Sun et al.
In situ synthesis of polymetallic Co-doped g-C₃N₄ photocatalyst with increased defect sites and superior charge carrier properties
Carbon
(2017)
S. Zhang et al.
Synthesis of boron-doped g-C₃N₄ with enhanced electro-catalytic activity and stability
Chem. Phys. Lett.
(2017)
G.M. Jiang et al.
Monodisperse bismuth nanoparticles decorated graphitic carbon nitride: enhanced visible-light-response photocatalytic NO removal and reaction pathway
Appl. Catal. B
(2017)
M. Faisal et al.
Synthesis of highly dispersed silver doped g-C₃N₄ nanocomposites with enhanced visible-light photocatalytic activity
Mater. Des.
(2016)
M. Wang et al.
Effective visible light-active boron and europium co-doped BiVO₄ synthesized by sol-gel method for photodegradion of methyl orange
J. Hazard. Mater.
(2013)
D. Xu et al.
Synthesis and photocatalytic performance of europium-doped graphitic carbon nitride
J. Rare Earths
(2013)

F. Wang et al.

Facile synthesis of N-doped carbon dots/g-C₃N₄ photocatalyst with enhanced visible-light photocatalytic activity for the degradation of indomethacin

Appl. Catal. B

(2017)

C.Y. Liu et al.

Chlorine intercalation in graphitic carbon nitride for efficient photocatalysis

Appl. Catal. B-Environ.

(2017)

S. Wang et al.

Controllable synthesis of nanotube-type graphitic C₃N₄ and their visible-light photocatalytic and fluorescent properties

J. Mater. Chem. A

(2014)

H. Gao et al.

Towards efficient solar hydrogen production by intercalated carbon nitride photocatalyst

Phys. Chem. Chem. Phys.

(2013)

W. Cui et al.

Highly efficient performance and conversion pathway of photocatalytic NO oxidation on SrO-clusters@amorphous carbon nitride

Environ. Sci. Technol.

(2017)

X. Wang et al.

A metal-free polymeric photocatalyst for hydrogen production from water under visible light

Nat. Mater.

(2009)

G. Zhang et al.

Iodine modified carbon nitride semiconductors as visible light photocatalysts for hydrogen evolution

Adv. Mater.

(2014)

X. Fan et al.

Improved photocatalytic activity of g-C₃N₄ derived from cyanamide-urea solution

RSC Adv.

(2015)

J. Wang et al.

Porous Mn doped g-C₃N₄ photocatalysts for enhanced synergetic degradation under visible-light illumination

J. Hazard. Mater.

(2017)

X. Chen et al.

Fe-g-C₃N₄ catalyzed oxidation of benzene to phenol using hydrogen peroxide and visible light

J. Am. Chem. Soc.

(2009)

Z. Ding et al.

Synthesis of transition metal-modified carbon nitride polymers for selective hydrocarbon oxidation

ChemSusChem

(2011)

Cited by (125)

Effect of P and Ce co-doping on the photocatalytic performance of g-C<inf>3</inf>N<inf>4</inf>: Experimental and theoretical studies
2024, Diamond and Related Materials
Element doping strategies are commonly employed to achieve effective photocatalysts. In this work, a novel form of P and Ce co-doped g-C₃N₄ nanosheets was synthesized using a one-step thermal polymerization technique, exhibiting remarkable efficiency in the degradation of organic pollutants under visible light. The prepared catalysts underwent comprehensive characterization through XRD, FT-IR, SEM, TEM, BET, XPS, UV–vis, PL, and electrochemical testing. The electronic and optical properties of the catalysts were further elucidated using first-principles density functional theory (DFT). In the photocatalytic experiment of degrading Rhodamine B (RhB), the photocatalytic ability of g-C₃N₄ nanosheets was improved at different degrees, among which g-C₃N₄ nanosheets co-doped with P and Ce showed the highest photocatalytic activity, with a degradation efficiency of 90.58 % for RhB. Furthermore, the photocatalytic mechanism was confirmed through free radical capture experiments. This study presents a novel approach for the development of efficient photocatalysts to remove pollutants.
Gram-scale synthesis of atomically dispersed p-block Al atoms on polymeric carbon nitride for efficient antibiotic photodegradation
2023, Applied Surface Science
Single-atom decorating polymeric carbon nitride (PCN) is often regarded as a class of promising catalyst for energy conversion and environmental remediation due to its ultrahigh atom utilization and unparalleled performance. Herein, gram-scale atomically dispersed p-block aluminum (Al) atoms on PCN photocatalyst (denoted as ACN) was successfully synthesized via a facile thermal polymerization strategy. Atomic-level, optical characterizations and band structure analysis unveil that Al atoms are uniformly dispersed on PCN framework, which can effectively optimize the band structure, accelerate the separation and transport ability of carriers, and then facilitate antibiotics photodegradation efficiency. Remarkably, the optimal ACN-2 exhibits superb removal rates (∼80%) and outstanding pseudo-first-order kinetic constants (0.084 min⁻¹, 0.051 min⁻¹ and 0.067 min⁻¹, respectively) over visible-light-induced degradation of tetracycline, oxytetracycline and chlortetracycline in just 20 min, and ca. 95% of the original removal rate can be maintained even in 10 consecutive TC degradation cycles, illustrating the superior stability and reusability of ACN-2. Notably, >30 g of photocatalyst (i.e., ACN-500) obtained via precursor amplification procedure still displayed excellent TC photodegradation performance. This work paves the way for practical application of an advanced single-atom Al-decorated PCN photocatalyst for pollutant remediation.
Design and construction of a double Z-scheme CdS@g-C<inf>3</inf>N<inf>4</inf>/Bi<inf>2</inf>MoO<inf>6</inf> ternary nanocomposite: Photocatalytic degradation in visible light, adsorption and electrochemical applications
2023, Materials Chemistry and Physics
Improved photocatalytic performances can be achieved by synthesizing double heterojunction nanocomposites with suitable conduction band (CB) and valence band (VB) edge potentials. In the current study, a hydrothermal approach was used to successfully synthesize a Z-scheme CdS@g-C₃N₄/Bi₂MoO₆ (CdS@GB) ternary nanocomposite with varied CdS contents. The photocatalytic efficiency of the as-synthesized materials was determined by studying the degradation of Rhodamine B (RhB) and Acetaminophen (ACM) pollutants. The experimental results revealed that 15 wt% CdS@GB (15CdS@GB) ternary composite showed the highest photocatalytic performance indicating 98.8 and 83% degradation of RhB and ACM in 35 and 140 min of irradiation, respectively. The stability of the ternary composite was also relatively high even after four consecutive cycles of photodegradation. The main reactive species involved in photodegradation processes was O₂^•- as revealed by the quenching experiments. The nitro blue tetrazolium (NBT) experiment further confirmed it, which showed the high production of O₂^•- in the reaction mixture. The synthesized ternary composites were used to study the dark adsorption of RhB, and the results confirmed the applicability of the Langmuir isotherm model. The electrochemical properties of the synthesized materials were investigated using electrochemical impedance spectroscopy (EIS) and cyclovoltammetry (CV). The results showed that 15CdS@GB has the lowest charge-transfer resistance and highest specific capacitance. Based on the findings, a double Z-scheme mechanism route was designed and presented to explain the photodegradation of the target pollutants.
Carbon chains modulate carrier transport in tubular graphitic carbon nitride for efficient photocatalytic degradation
2023, Solid State Sciences
In recent years, environmental wastewater has become an increasingly prominent problem, and photocatalytic degradation is one of the effective means to treat waste pollutants. In this study, glycine was embedded in a tubular carbon nitride material with melamine as the parent by a supramolecular self-assembly strategy to prepare carbon chains implanted tubular graphitic carbon nitride (CTCN). The introduction of carbon chains can reduce the formation of hydrogen bonds, which is beneficial to improve the carrier transport efficiency. It can also adjust the valence band position and has better reduction performance. The thin-walled tubular structure formed by supramolecular self-assembly exposes more active sites and shortens the carrier transport distance due to the size effect, which further improves the carrier separation efficiency. The synergistic effect of the two greatly contributes to the photocatalytic performance of the material. The degradation rate of 0.3% CTCN is 8.1 times higher than that of Bulk CN, and 0.3% CTCN exhibits good stability. This solution is beneficial to optimize some existing wastewater treatment methods and has a role in environmental protection.
Largely elevated photocatalytic hydrogen generation over Eu doped g-C<inf>3</inf>N<inf>4</inf> photocatalyst
2023, International Journal of Hydrogen Energy
Graphitic carbon nitrides (g-C₃N₄) have come into researchists’ horizons for their diversified merits, such as the especial graphite-phase 2D laminar framework, competitive price, innoxious, eligible bandgap (∼2.7 eV) and acceptable consistency. Whereas limited by the disadvantages of inferior specific surface area and fast recombination of photo-generated charge pairs, the pragmatic applicability of g-C₃N₄ turns out to be still lacking. In our work, g-C₃N₄ (GCN) and Eu-doped g-C₃N₄ (Eu/CN) with different Eu/g-C₃N₄ molar ratios (1%, 2%, 3%, 4%) were synthesized by an impregnating method and characterized through a series of measurements. Photocatalytic activities of Eu/CN catalysts manifest preeminent H₂ generation capacity and stability excited by solar light. The highest H₂ generation rate without any co-catalyst is 128.8 μmol g⁻¹ h⁻¹ over the 3% Eu/CN, achieving 117.1-fold as high as that of GCN (1.1 μmol g⁻¹ h⁻¹). Eu doping is proven to slightly widen the bandgap of the samples, resulting in the conduction band of samples more negative and the reduction reaction more effortlessly. Simultaneously, Eu doping changes the molecular structure of g-C₃N₄ and forms more nitrogen defects. Photo-excited electrons can be captured by the defective sites derived from the defect levels, and the recombination rate of photoinduced carriers will be significantly inhibited, accordingly facilitating the high-efficiency separation of photo-induced carriers and improving photocatalytic efficiency. This study provides an advantageous instruction for the implementation of rare earth metals application in improving the separation and transfer rate of photo-induced electrons (e⁻) and holes (h⁺) over g-C₃N₄.
Construction of heterogeneous structures of MIL-101(Fe)/Ce/g-C<inf>3</inf>N<inf>4</inf> nanocomposites for enhanced photocatalytic activity under visible light
2023, Journal of Solid State Chemistry
A heterostructured MIL-101(Fe)/Ce/g-C₃N₄ (MCCN) composite was designed and synthesized by solvothermal method. The composite was characterized by XRD, SEM, EDS, FT-IR, BET, XPS, UV–Vis DRS, PL and EIS. The MCCN photocatalyst exhibits superior photocatalytic performance for the degradation of rhodamine B (RhB) and methylene blue (MB), and the efficiencies are found to be 90.36% and 88.17%, respectively. The kinetic constants k of MCCN-3 against RhB and MB dyes are 0.04094 min⁻¹ and 0.03319 min⁻¹, respectively, under visible light for 75 min irradiation. The improved degradation efficiency of MCCN attributed to the enhanced light absorption and the transport channels of electron-hole pairs by forming a heterojunction between MIL-101(Fe) and Ce/g-C₃N₄ with a favourable band position. Moreover, the possible mechanism of photocatalytic degradation of dyes was proposed though free radical trapping experiments. This work provides an effective way for constructing novel visible-light-driven photocatalyst in the removal of organic molecules from waste water.

View all citing articles on Scopus

View full text

Synthesis of hollow lantern-like Eu(III)-doped g-C3N4 with enhanced visible light photocatalytic perfomance for organic degradation

Highlights

Abstract

Introduction

Section snippets

Photocatalyst preparation

Structure and morphology

Conclusions

Acknowledgements

J. Hazard. Mater.

J. Alloys Compd.

J. Catal.

Carbon

Carbon

Chem. Phys. Lett.

Appl. Catal. B

Mater. Des.

J. Hazard. Mater.

J. Rare Earths

Appl. Catal. B

Appl. Catal. B-Environ.

Controllable synthesis of nanotube-type graphitic C3N4 and their visible-light photocatalytic and fluorescent properties

J. Mater. Chem. A

Towards efficient solar hydrogen production by intercalated carbon nitride photocatalyst

Phys. Chem. Chem. Phys.

Highly efficient performance and conversion pathway of photocatalytic NO oxidation on SrO-clusters@amorphous carbon nitride

Environ. Sci. Technol.

A metal-free polymeric photocatalyst for hydrogen production from water under visible light

Nat. Mater.

Iodine modified carbon nitride semiconductors as visible light photocatalysts for hydrogen evolution

Adv. Mater.

Improved photocatalytic activity of g-C3N4 derived from cyanamide-urea solution

RSC Adv.

Porous Mn doped g-C3N4 photocatalysts for enhanced synergetic degradation under visible-light illumination

J. Hazard. Mater.

Fe-g-C3N4 catalyzed oxidation of benzene to phenol using hydrogen peroxide and visible light

J. Am. Chem. Soc.

Synthesis of transition metal-modified carbon nitride polymers for selective hydrocarbon oxidation

ChemSusChem

Synthesis of hollow lantern-like Eu(III)-doped g-C₃N₄ with enhanced visible light photocatalytic perfomance for organic degradation

Controllable synthesis of nanotube-type graphitic C₃N₄ and their visible-light photocatalytic and fluorescent properties

Improved photocatalytic activity of g-C₃N₄ derived from cyanamide-urea solution

Porous Mn doped g-C₃N₄ photocatalysts for enhanced synergetic degradation under visible-light illumination

Fe-g-C₃N₄ catalyzed oxidation of benzene to phenol using hydrogen peroxide and visible light